​BASSET HORN (Fr. Cor de Basset, or Cor de Bassette; Ger. Bassethorn, Basshorn; Ital. Corno di Bassetto), a wood-wind instrument, not a "horn," member of the clarinet family, of which it is the tenor.

Fig. 1. (From photographs lent by M. Victor Mahillon.)

The basset horn consists of a nearly cylindrical tube of wood (generally cocus or box-wood), having a cylindrical bore and terminating in a metal bell wider than that of the clarinet. For convenience in reaching the keys and holes, the modern instrument is usually bent or curved either near the mouthpiece or at the bell, which is turned upwards. The older models were bent in the middle at an obtuse angle, and had at the bottom of the lower joint, near the bell, a wooden block, inside which the bore was reflexed, and bent down upon itself.[1] The basset horn has the same fingering as the clarinet, and corresponds to the tenor of that instrument, being pitched a fifth below the clarinet in C. The alto clarinet in E♭ is often substituted for the basset horn, especially in military bands, but the instruments differ in three particulars:—(1) The basset horn has a metal bell instead of the pear-shaped contracted bell of the alto clarinet. (2) The bore of the basset horn is wider than that of the alto clarinet in E♭, or of the tenor clarinet in F. (3) The tube of the basset horn is longer than that of the clarinet, and contains four additional long keys, worked by the thumb of the right hand, which in the clarinet is only used to steady the instrument. These keys give the basset horn an extended compass of two tones downwards to F whereas the E♭ clarinet only extends to G and the F clarinet to A (actual sounds). This brings the compass of the basset horn to a range of four octaves from , actual sounds . ​Like the clarinet, the basset horn is a transposing instrument, its music being written a fifth higher than the actual sounds. The treble clef is used in notation for all but the lowest register. The technical capabilities of the basset horn are the same as for the clarinet, except that the extra low notes from A to F (actual sounds) can only be intoned slowly and staccato; the notes of the upper register being better represented in the clarinet are seldom used in orchestral music.

The tone of the basset horn is extremely reedy and rich, especially in the medium and low registers; the tone colour is similar to that of the clarinet without its brilliancy; it is mellow and sensuous, but slightly sombre, and therefore well adapted for music of an elegiac funereal character.

The basset horn flourished mainly in Germany, where at the end of the 18th century it was the favourite solo instrument of many celebrated instrumentalists, such as Czerny, David, Lotz, Springer, &c. Among the great masters, Mozart seems to have been foremost in his appreciation of this beautiful instrument. In his Requiem, the reed family is represented by two basset horns having independent parts, and two bassoons. Mozart has also used the instrument with great effect in his opera La Clemenza di Tito, where he has written a fine obbligato for it in the aria "Non piu di Flori"; in Zauberflöte; and in chamber music, viz. short adagio for two basset horns and bassoon, and another for two clarinets and three basset horns (Series 10 of Breitkopf & Härtel's complete edition). Beethoven employed it in his Prometheus overture. Mendelssohn used it in military music, and in two concerted pieces for clarinet and basset horn with pianoforte accompaniment, in F and D min., opp. 113 and 114, dedicated to Heinrich and Carl Bärmann.

The archetypes of the basset horn are the same as those of the clarinet (q.v.). The basset horn was the outcome of the desire, prevailing during the 16th and 17th centuries, to obtain complete families of instruments to play in concert. The invention of the basset horn in 1770 is attributed to a clarinet maker of Passau, named Horn, whose name was given to the instrument;[2] by a misnomer, the basset horn became known in Italy as corno di bassetto, and in France as cor de basset. In 1782, Theodore Lotz of Pressburg made some modifications in the instrument, which was further improved by two instrumentalists of Vienna, Anton and Johann Stadler, and finally in 1812 by Iwan Mueller, a famous clarinettist, who invented the alto clarinet in E♭ from the basset horn, by giving the latter a construction and fingering analogous to those of the clarinet in B♭, which he took as his model, instead of the clarinet in C.